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DAC3482: How to connect Dual dac output to two IQ modulators

Izik
Expert 1585 points
Part Number: DAC3482
Other Parts Discussed in Thread: TRF370417

Hello 

I am using DAC3482 as an IQ modulation source in my system. 

I connect the DAC outputs to IQ mod TRF370417, Since I need to use the same modulation but with different LO's I thought to use the same dual dac to drive two IQ modulators simultaneously.  I don't want to use quad dac in order to save power and money. 

I know that the matching circuit and the shape filter needs to be adjusted to match the common mode voltage and dac and the two IQ mod input impedance in parallel. 

Can you please help? 

Thanks

Izik

  • 0
    TI__Genius 12965 points
    Izik,

    In general it is not a good idea to drive 1 common IQ source into 2 IQ modulators. The problem is that there will be different analog impairments for each IQ modulator and you cannot do any compensation or correction in the DAC or digital baseband to correct for it. If you are ok with this then you can try this. This is something we have not tried before.

    For interface designs have a look at this TI design. You can try to simulate this in TINA 1st to ensure you meet all of the common mode, compliance requirements.
    www.ti.com/.../TIDA-00077

    Ken.
  • 0 in reply to Ken C
    Expert 1585 points
    Hi Ken

    I can do the compensation on the modulator side. Are there any other concerns?

    Thanks
  • 0 in reply to Izik
    TI__Genius 12965 points
    Izik,

    As long as the compliance voltage and common mode are met on both the DAC output and modulators inputs, then it should be ok.

    Ken.